It's worth noting that in some parts of the world (including the US) there are days which are 23 hours long and others which are 25 hours long, which occur when

It's worth noting that in some parts of the world (including the US) there are days which are 23 hours long and others which are 25 hours long, which occur when daylight savings time starts and stops. (I'm guessing your calendar isn't high resolution enough to worry about leap seconds.) So if I'm reading your code aright, the timestamp will be off by an hour on two Sundays a year in places where DST is observed. But to answer your original question, I'd have to say it depends. If the clever stuff is really much more efficient, or less likely to break in unusual circumstances, I say use it, but document it carefully. Otherwise, best to code it clearly.